This invention pertains to air vent valves, in general, and to radiator vent valves of the type used in one-pipe steam heating systems, in particular.
Each radiator, unit heater, or convector and each steam main end in a one-pipe heating system must be equipped with an air vent valve to allow proper steam circulation.
Air vent valves used in one-pipe steam heating systems are required to meet several exacting criteria. For example, the valve must be capable of permitting the passage of air from the heating unit, but at the same time must close off when steam or water reaches it. In addition, as soon as the water recedes, or after the temperature inside the vent valve has fallen, it must open once again to permit the passage of air. Radiator vent valves must be capable of operating continuously during a heating season, therefore, the materials used must be corrosion resistant and preferably of relatively low cost.
Prior radiator vent valves such as those of U.S. Pat. Nos. 2,167,433 and 2,338,495 have been equipped with a brass float, filled and sealed with a liquid that expands under heating to thereby close off a port when steam reaches the valve. At the same time the float is bouyant in water and therefore shuts off the port on water rise.
The foregoing type of construction of radiator vent valves has been effective and has provided numerous advantages. However, because of required continuous operation during a heating season and the soaring cost of energy, the aforementioned construction has proved to be unreliable and therefore is replaced yearly with a consequent increase in cost.
Other prior vent valves such as that of U.S. Pat. Nos. 2,084,256 and 2,144,097 utilize a float filled with an expansible-contractable temperature responsive fluid as in the aforementioned patents and further include a bellows filled with a temperature responsive fluid which is responsive to lower temperatures. Such vent valves utilize cylindrical shaped floats and require the use of guide pins attached to the float to prevent joining the float.
U.S. Pat. No. 379,889 shows a vent valve utilizing a cylindrical float and a wire coil. The float is guided within the coil and rises to close a vent port when water enters the valve. The wire coil expands at steam temperature to close the vent port. The wire coil and the float operate independently of each other.
U.S. Pat. No. 312,042 shows a vent valve having a hollow spheroidal float of rubber which floats in the presence of water and expands under the heat of steam. This arrangement does not appear to be quickly responsive to steam and the life of a rubber float is relatively short.
U.S. Pat. No. 3,260,458 uses a ball valve and sleeve arrangement actuated by a bimetallic strip to close a vent under the heat of steam. However, this arrangement does not prevent spitting of water.